The invention relates to a tripod joint having an outer joint part with three circumferentially distributed, axis-parallel recesses which form circumferentially distributed opposed tracks. An inner joint part having a star-shaped cross-section and three circumferentially distributed arms engaging the recesses in the outer joint part. The arms support roller assemblies. Each roller assembly includes a roller carrying assembly and a roller. The roller, with respect to the arm, is axially movable relative to the arm axis and angularly movably pivotable relative to the arm axis.
Tripod joints which provide movability are described, for example, in DE 28 31 044 (Honda), DE 39 36 601 (GKN) and DE 37 16 962 (NTN).
When the joint rotates in an articulated condition with reference to the inner joint part, there occurs radially oscillating movement of the rollers relative to the axis of the inner joint part and pivoting movement of the rollers on the arms. At the same time, during the articulated condition with reference to the outer joint part, there occurs longitudinally extending oscillating rolling movement of the rollers along the tracks. The first mentioned radial and pivot movements are accompanied by sliding friction whereas the next mentioned movements are predominantly rolling contact movements. Because of said friction forces, prior art tripod joints with an increasing angle of articulation, are subject to a considerable increase in joint excitation forces, e.g. cyclic forces generated in the joint and transmitted to the driveline. Because of the wear caused in the driveline and the development of noise, such forces are highly undesirable.
In addition, in some cases such joint excitation forces scatter from joint to joint, sometimes even within the individual joint during operation. The cause of the scatter may be an unstable behavior of the roller in the tracks of a joint rotating in the articulated condition. This may lead to different and changing contact and friction conditions on various contact faces of the roller assembly relative to the recesses.